Insulation displacement contacts are widely used for interconnecting electrical wire, particularly fine wires utilized for transmitting signals in computers, business machines, and the like. A wide variety of such contacts have evolved to include features like the prior art contact 10 shown in FIGS. 4 and 5. There, contact 10 is formed of flat conductive sheet material to include a pair of upstanding blades 12 and 14 having centrally disposed slots S. Leading to the slots S are tapers T and at the bottom of each slot is a bight B. The blades 12 and 14 extend upwardly, essentially at right angles to a base 16, which is shown in FIGS. 4 and 5 to be limited to the plates 12 and 14; it being understood that typically the base 16 may extend fore and aft of such blades to be joined to a wire strain relief in a manner to be described and to a further part of the contact used for interconnection purposes.
With respect to the blades 12 and 14, the tapers T serve to position and guide the insertion of a wire 17 having a conductive core 18 of solid or stranded wire surrounded by an insulating sheath 20. The slots S are given a width less than the diameter of the conductive core 18, and the thickness of the blades 12 and 14, in conjunction with the edges of the slots, serve to cut and therefore strip the insulation sheath 20 sufficiently for the edges of the slots S to deform the wire and form a low resistance, stable electrical interface or connection with the core 18. As can be seen in FIG. 5, the conductive core 18 is positioned within the slot S at a point removed from the bight B. Care must be taken with respect to the contact shown in FIG. 4 and to similar contacts that the core is not pushed downwardly upon loading the wire in the contact to a point wherein the bight B cuts into the wire and severs either strands or the wire core itself.
In FIG. 6, a further prior art representation is shown of an electrical contact 30 which includes a base 31, analogous to the base 16 heretofore referred to and extending forwardly a spring contact 32 which would engage a further contact, not shown, such as a pin or post in a connector. As can be seen, an insulation displacement portion 34 includes a pair of blades 33 and 35 which have the characteristics heretofore described with respect to FIGS. 4 and 5. The wire 17 can be seen to be inserted in insulation displacement portion 34. To protect the connection made in the insulation displacement portion 34, a strain relief 36 is provided from material struck out of the base material from which 31 is formed and folded, or crimped, down on the wire as shown in 36. As can be seen, the wire 17 is pushed down against the base 31, forming a bend 38 in the wire. This has been found to create stresses in the wire which can interfere with the interconnection between the wire core 18 and the slots in the insulation displacement blades. Furthermore, the fact that there is a bend, a difference of height relating to the different parts of the wire, can result in a sensitivity making it more difficult to avoid pushing the wire core into engagement with the bight, as discussed in the contact presented in FIGS. 4 and 5.
Accordingly, it is an object of the present invention to provide an insulation displacement type contact having an improved wire strain relief incorporated in the contact in relation to insulation displacement slotted blades. It is a further object to provide a contact having an insulation displacement portion in conjunction with a wire strain relief which is adjustable from design to design to fix the height of the wire relative to the base of the contact. It is yet a further object to provide a wire strain relief which is resilient and which positions a wire in essentially a straight line relative to a contact base to preclude strains and stresses to the interconnection made in insulation displacement contact.